I have a Dual CF to IDE adaptor. I have a Kingston 16GB and 32GB card. Vista requires 20GB to install but no matter how I install them in the adaptor and no matter how I arrange the boot order in the bios Vista will only show the 16GB drive as an option for installation, which then fails as there is not enough memory. I have tried formating them as Fat32 and NTSF but nothing works. Any suggestions?

Part of the point of new file systems is to be able to use files larger than 4GB. fat32 cant do this. Exfat can, but its not open (although i think microsoft is who owns it). NTSF is what you want. And if you are using IDE, you need to make sure your bios is set to IDE or legacy, and NOT RAID or AHCI. you should not needany drivers during install if set to IDE or Legacy.

If that is all correct, i would try looking at the CF drives in an already booting computer. if they cant be seen, go into disk management and do a full reformat (not quick) in NTSF. then make sure the disk mounts and can be read and write to.